TRANSACTIONS OF SECTION B. 



523 



quarter of the present centuiy, tut these were rather of a mechanical than of a 

 chemical nature. They chiefly owed their origin to the lessons taught by the 

 chemist Black to James Watt, who profited by them in the application of steam as 

 a motive power. This brings us to the year 1828, a year which will always be 

 distinguished in the annals of the iron trade, by the di.scovery of Neilson of the 

 value of heated air in smelting the ores of this metal. I never heard it maintained 

 that this inventor had any pretensions to be considered a man of science. Had it 

 been otherwise, the knowledge of the virtues of the hot blast might have been 

 indefinitely postponed, and this opinion is founded on the fact that for many a long 

 year no satisfactory explanation was given why heat, obtained bj' burning coal, in 

 the hot air apparatus was capable of saving three or four times its weight in the 

 fuel consumed in the furnace itself. I propose, with your permission, to consider 

 this subject with more attention than I shall devote to other portions of this 

 address, and I am led to do this, not only because it is one of some scientific 

 interest, but because its study seems to afford a solution to some questions in 

 respect to which great diflerences of opinion prevailed among those whose daily 

 work led them to pay much attention to their details. These questions have all a 

 reference to the quantity of fuel consumed in smelting the ore, as this may be 

 aflfected by the temperature of the blast and the dimensions of the furnaces 

 employed for this purpose. 



As is well understood, the heat excited in an iron furnace may be classified 

 under three heads : — 



First, that derived from the combustion of the coke at the point where the 



blast enters the furnace, the ultim.ate product being carbonic oxide. 

 Second, the conversion of a portion of this carbonic oxide into carbon 



dioxide. 

 Third, the heat carried into the furnace by the blast. 



For the better illustration of the relations which the heat derived from these 

 sources bear to one another, a table (No. ]) has been prepared in which the quanti- 

 ties of each are given in centigrade calories, and reckoned upon 20 units of iron to 

 correspond ^vith English weights. The information upon which the calculations 

 are based is derived from actual observation gathered from furnaces of different 

 sizes and fed with air at different temperatures. 



A second table contains statements showing the manner in which the heat so 

 generated is appropriated in the various divisions of the duty the furnaces had to 

 perform, and for facility of comparison, alongside the quantities of heat so required, 

 their equivalents in the coke used have been added. 



In the table No. II. the appropriation of the heat is separated into Constants 

 and Variables. The first consists of items where the quantity of heat required in 

 making a particular quality of iron is only liable to alterations of trifling amount. 

 On the other hand the variables exhibit in A and B differences so considerable that 

 ■work which in the furnace blown with cold air absorbed 73,388 calories per 20 cwts. 

 of pig-iron was done with 58,645 calories by merely raising the blast to 485°. 



Table I. 



